Art of combustion



ART oF coMBUsTIoN Filed Dfi. 27, 1937 2 Sheets-Sheet l INVENTORs. farizzMuelle 620/ e 'Ii' /Yezarza TTORNEY Oct.. 29, 1940. M. 1 MUELLER Er A1.

ART OF COMBUSTION Filed Dec. 27,Y 1957 VIZ Sheets-Sheet 2 r l DARNEYPatented Cet. 29, 1940 PATENT f oEElcE 2,219,696 ART or coMUsrroN MoritzL. Mueller, Grosse Pointe, and George R. Neumann, St. Clair Shores,Mich., assignors to Borg-Warner Corporation, Chicago, Ill., acorporation of Illinois Application December 27, 1937, Serial No.181,752

This invention relates in general to the art of combustion,withparticular referencetoan apparatus and method for burning fluidhydrocarbons. Such fluid hydrocarbons will hereinafter be described asoil or fuel oil although it is to be understood that gaseous or otherfluid hydrocarbons may fall within the scope of the description.

Heretofore, apparatus which has' employed n pressure for atomizing fueloil by spraying it through a fine nozzle has depended for the most partupon releasing the sprayed oil fog into a combustion chamber and uponthe directing of a stream of air into the combustion chamber as s asheath around the oil fog to secure proper mixing or comingling of theparticles of oil and air. Such apparatus has relied upon means for-directing the air in such a manner that the sheath or envelope of airprojected into the comn bustion chamber will coincide with and fit overthe cone of oil fog issuing from the nozzle` tip. It has been recognizedthat this is a very delicate adjustment and that slight inaccuracy ofthe nozzle, slight displacement of one part rela- 5 tive to another, anddifferences in the quality of fuel oil, which may be delivered by thelocal fuel dealer, will result in anupsettingof this adjustment and anaccording loss in emciency of the combustion apparatus. Such priorcombustion apparatus has also been at great pains to produce agitationor whirling movement of the air projected into the combustion chamber inorder that the cone of oil and the sheath of air may be more thoroughlymixed. Attempts have also been made to give the oil and air whirlingmovements in reverse directions in order to assist in this mixing. Allsuch constructions attempt to mix oil and air in the combustion chamberafter the pressure has been released from both of these substances andafter their velocity has become relatively small and to this end haverequired the use of special combustion chambers for each burner orchanges to be made in the burner to t it for operation in various 5shapes of combustion chambers.

The requirements for precision in adjustmentI and the delicacy of suchadjustments have made such equipment undesirable for domestic or smallcommercial installations where there is no skilled 50 operator on handto keep constant check on the condition of the apparatus. As a result,the majority of such installations are constantly running below theirmaximum elciency, and such lack of efficiency is reflected in higherfuel bills 55 which the consumer is required to pay.

,in connection with this burner without any alteration in the firecharacteristics. I

With these purposes in mind, it is an object of the invention g toprovide means for mixing a sprayed oil fog and air within a pressurearea prior to releasing the mixture to a combustion chamber.

A further object of the invention is to provide a new method of burningcombustible. fluids withextremely high efficiency.

An additional object of the invention is to provvide a head forinsertion in present day oil burning apparatus which will providemeansfor realizing the advantages outlined above.

It is a still further object of the invention to supply means forcontrolling the shape of the fire independent of any particular shape ofcombustion chamber.

Itis a further object of the inventionA to pro-` vide an oil burner headwhich is simple, sturdy, readily and cheaply manufactured and which ef'fectuates the foregoing objects and realize the advantages set forthhereinafter.

To this end, apparatus embodying the invena5 tion will be seen to residein an oil burning apparatus of the pressure atomizing gun type. Suchapparatus usually consists of a blower which is operated by an electric,motor and which d charges a blast of air along a draft tube. In

most installations. the draft tube carries, besides the air, a fuel pipewhich 'is supplied with fuel oil under pressure by means of a pumpactuated by the blower motor, and a pair kof electrodes for' ignitingthe fuel and air. In most instances, the draft tube is providedintermediate its length with a baille which causes the air to take apath adjacent the inside diameter of the tube and results in the highpressure space in the draft tube being located at the blower side of thebaille. As a result of the use of this baille, air which ows past theoil nozzle is of somewhat reduced pressure and can notserve effectivelyto entrain the oil. Because Aof this low pressure,'various expedientshave been resorted to at the combustion chamber end oi a burner in anattempt to give' drical head. The pressure baille, which is locatedintermediate the ends of the draft tube, is removed so as to extend thespace under high pressure within the draft tube forwardly to a pointWithin the newly inserted burner head. With such a construction, the airflowing past the burner nozzle is of the full pressure delivered by theian and has an accordingly great ability to entrain the oil issuing fromthe nozzle.

The oil being sprayed by th'e oil nozzle takes the shape of a right conewhich has its apex at the oil nozzle aperture.-

past the nozzle is deflected just forwardly thereoi' into a conical pathwhich has its apex out beyond or forwardly of the oil fog apex, thesetwo aplces being oppositely directed and lying upon a line which formsthe common altitude of the cones.

The angle of the oil nozzle upon which the which may be either Thearrangement of the cones oi the oil fog and of the air stream is suchthat the two meet one another with the elements of free floatingposition.

In the drawings, in which similar reference 60 characters are employed'to designate similar parts and of which there are two (2) sheets:

a plane as indicated by the line 4 4 of Fig. 3, and

'75 looking in the direction of the arrows;

Air which is being fedY spaced points.

Fig. 5 is a vertical sectional view through the oil burner takensubstantially upon a plane as inthe direction of the arrows;

Fig. 6 is a right end elevational view of the part of the oil burnershown in Fig. 2.

Fig. 'l is a side elevational view of a different BITOWS; and,

is formed toward its rear end with a shell i8 for 3( enclosing a bloweri6 of the sirocco type which is pump (not shown) which supplies oilunder pres- 35 sure to' a i'uel pipe 22 extending through a draft tube24 to supply oil to a. nozzle 26. The fan pulls air into the shell I8and discharges it along the draft tube 24.

Toward its forward end the fuel pipe 22 is sup- 40 ported by means of atripod the inside diameter of the draft tube at three Tripod 28 may alsosupport a pair of electrodes 30 which comprise conductors having tips 32located adjacent the oil nozzle, suoli 45 The draft tube 24, which iscylindrical, receives in its forward end a burner head indicatedgenerally at 36. The burner head 36 comprises a 55 portion 38 and inflange for draining liquids which may be 30 extending completely aroundthe cylin- The cylindrical surface of the cylindrical portion 38terminates 70 from left to right, as viewed in Fig. 2, toward thecoinciding axes of the draft tube 24 and head 36. The head I6 may becentered with respect to the 76 flowing through the draft tube at apressure off draft tube 24 and permanently held thus located by means ofspaced set screws 58 threaded into the'draft tube 24 and engaging theouter surface of the cylindrical portion 38 of the burner head 36.

The'concal portion 48 of the burner head 36 terminates in a shortcylindrical portion 52 forming an aperture through which the air flowsto entrain the oil. Forwardly of the cylindrical portion 52, the burnerhead is provided with a flat annular surface 54 and with a series ofapertures 56 which extend radially through the cylindrical portion 38 ofthe head 36. 'I'he apertures 56 are uniformly spaced around theperiphery of the head and provide a means for supplying air to the oiland air mixture issuing from the main` aperture 58 defined by the shortcylindricalsurface 52, in which the conical portion 48 of the headterminates. As previously explained, these supplementary air supplyingpassages result in a retarding of the velocity of the flame. vIt hasbeen found that a decrease in the total area of the apertures 58 withrespect to the area of the 'aperture 58 will result in the flamepropagated by the burner becoming longer and in its standing at adistance further removed from the burner head after the flame has beenestablished and ignition by means of the electrodes 32 has beendiscontinued.

The apertures 56 also serve to prevent eddy currents in the mixture ofoil and airfrom wiping the flat face 54 of the burner. It has been foundthat if apertures 56 have too little area with respect to the oriilce58, they still will not prevent this wiping of the mixture upon the flatface 54. Such an action on the part of the mixture of oil and air isundesirable, since it is apt to leave deposits of oil upon this face,which in time would become partially burned and would car- 40 bonizethis face of the burner, requiring it to be frequently cleaned. Byenlarging the orices 56 the face 54 is scoured with air and "carbondeposits thereupon are prevented.

The oil nozzle 26 is centered with respect to the 45 circular aperture58 by means of a tripod, the

central portion 68 of which surrounds and supports the fuel pipe 22 andthe legs 62 of which engage the inside surface of the cylindricalportion 38 of the hea-d 36. The oil nozzle 26 may be 50 adjustedrearwardly or forwardly with respect to the aperture 58 by loosening a.set screw 64 threaded into the central hub 60 of the tripod.

This adjustment, made in conjunction with a consideration of the angleA, formed by the oil 55 sprayed from the nozzle, determines the positionwhich the cone of oil issuing from the nozzle will take with respect tothe conical surface 48, which directs the, air stream against the oilstream.

Various tips may be used on the fuel nozzle havl 60 ing differentangularities, varying from thirty degrees to ninety degrees and varyingin the capacity or quantity of fuel which they will feed per hour. Ithas been found that it is relatively unimportant just what angle of fuelcone is' em- 65 ployed, as long as the air which is. supplied to thecentral mixing point has sufficient velocity to deilect this oil coneand prevent particles of oil from impinglng upon the conical surface 48or the cylindrical surface 52. With the air pressures 70 which areusually available in domestic installations ithas been found that theangle of the oil cone and the distance of the tip 26 rearwardly ofaperture 58 may be such that, were no air flowing through the drafttube, the oil might impinge 75 slightly upon the conical surface 48.With air about 0.30 inch of water, lthe air stream will act to compressand deflect the oil fog to prevent its striking the conical surface 48or the cylindrical surface 52 of the aperture 58. Higher air pressuresmay be employed, ranging upward to 4.0 inches of water.

The oil will flow from the pressure atomizing nozzle 26, as indicated bythe dotted line arrows .in Fig. 2, in such a manner that it wouldimpinge upon the edges of the orifice 58 were it not for the presence ofthe stream of air, as indicated by the fullline arrows in Fig. 2, whichserves to condense or compress the oil fog where it reaches a pointadjacent the orifice 58. After passing through the orifice 58, thearrows indicating the oll and air are seen to remain in their compressedstate until after they have passed the combustion chamber end or mouthof the burner, at which point they begin toV expand. Just after leavingthe oriflce 58, the stream of oil and air is joined by the supplementaryair, which flows through the apertures 56, as indicated by the full linearrows in Fig. 2.

It will be noted that the cone of oil fog is expanding as it passesthrough the orifice 58, whereas the cone formed by the air stream iscontracting and that the paths of particles located in the two streamsat their point of contact are directed transversely to one another, thusproducing a thorough penetration of each particle of the air stream intothe oil stream and a corresponding thorough penetration of each particleof the oil fog into the air stream. 'Ihe visible effect of this meetingof the two streams is that the oil stream, which is the only portionwhich may be seen, is somewhat compressed and turbulent as it passesinto aperture 58 and as it issues therefrom, becomes more turbulent andexpands slightly.

The apertures 56 inject air transversely of the mixture path andradially into the mixture of oil and air as it issues from the mouth ofthe orifice 58 and tend further to increase the turbulence of themixture at this point. The air supplied by apertures 56 also tends toconstrict the air and oil mixture and prevent its expansion in so rapida fashion that it would strike the inner corners 66 of the flangedportion 48 of the burner head 36 or its associated cylindrical portion61. Although this air is used to increase the turbulence at the mouth ofthe orifice 58, a portion of it is deflected and follows along theexterior of the fluids issuing from the burner mouth to form a sheetwhich entirely surrounds the flame and which is available during otheprogress of the combustion fluids through the combustion chamber for thecompletion of combustion;

The angle of the apex of the conical surface 48 determines to someextent the shape Yof the re. When this angle is relatively great, thatis, when it approaches 180, the fire will become very short and ofrelatively great diameter. As this conical angle is decreased, the flamebecomes relatively long andthin.

'I'he orifices 56 may be varied to cause a deflection of the flame inany desired direction. For example, if it is desired to raise the flamefrom the floor of the combustion chamber and have it stand in a moreelevated position with respect to the mouth of the burner than would bethe case when using the head as shown in Fig. 2, it is only necessary toenlarge the orifices 56 upon the lower side of the head 36 so as toincrease the amount of air owing through such lower orifices,

-the amount of air `flowing through the upper orices 56 remaining thesame. This enlargement of the lower orifices results in the flame beingdeected upwardly. It will be recognized that the flame can thus bedeflected in any desired direc- 5 tion, simply by increasing the size ofthe orifices 56 uponthat side of thehead which lies opposite to thedesired direction of deflection.

Upon starting, the electrodes 32 are energized to cause a spark totravel between them, and this l spark serves to ignite a portion of theoil and air within the burner head, such ignited fuel being carried outinto the combustion chamber by the oncoming air to establish ignition ofthe main flame. During this stage of combustion, the flame will beburning directly from the mouth of the burner, but after the ignitionhas been cut off, usually about ninety seconds after initiation ofburner operation, the flame will be self-propagating and will standabout two or three inches from the combustion chamber end or mouth ofthe burner, thus reducing the possibility of carbon depositing on theburner parts.

"I'he flame thus established, after cessation of the electric ignition,takes a shape somewhat as shown in Fig. 3. 'I'his flame appears to be asomewhat cylindrical mass of fire which is swelled slightly toward itsforward end, and, upon inspection, is seen to comprise an inner hollowcylindriical portion 10 of very brightly burning carbon particles whichforms the main portion of .the flame and an outer hollow cylindricalportion 12 somewhat more nebulous than the inner portion 10 and notquite so bright.- In the hollow interior T4 of the inner portion andbetween the cylindrical portions 'I8 and 12, there may beA a few tagends of nre, but the flame in the main is confined to these two paths.The llame is found upon inspection to be of a uniform dark yellow orlight orange color from one end to the 40 other, thus indicating thatits carbon dioxide content is all uniformly high and that combustion istaking place in a uniformly efficient manner.

This uniformity of the name tends to substantiate the theory that theair supplied from the ports 56 is useful as secondary air to completecombustion throughout the flame as well as to increase the turbulence ofthe air and oil mixture at its point of issuance from the orifice 58. Inthe usual flame propagated by the pressure atomizing gun type of burner,the ends of the flame are somewhat ragged and the colol of the flamevaries considerably from one end to the other, having a bright yellowcolor at the end '55 nearest the mouth of the burner, a dark yellow or alight orange color in its central portion, and a smoky dark orange colorat its ends. These colors are interpreted as follows:

60 Color: CO2 content (Per cent) Bright yellow 4- 5 Dark yellow orlightl orange 12-13 Smolq/ or dark orange 14-15 A uniformly high carbondioxide content is indicative of very eflicient combustion and tests offlue gas taken on products of combustion generated by a burner of thistype yield readings on CO2 content ranging from 12% to 14%, while the COcontent is zero and the O2 content approximately 4% or 2%, respectively.

In Figs. 7 to 9, there is shown a burner employing the head of thisinvention which is arranged to 'supply a mixture of fuel and air to avertically extending combustion chamber, such a combustion chamber beingof the type usually found in domestic installations which are desired tobe converted from solid fuel consuming to oil consuming heating plants.

Furnaces of this type usually embody acylindrical or rectangularcombustion chamber 80, 5 the walls 82 of which serve as heat transfersurfaces for transmitting the heat generated within the combustionchamber to a fluid heating medium lying upon the opposite side of thewalls 82. The grates (not shown) which are usually 10 present in solidfuel combustion apparatus, are removed and a floor 84 of refractorymaterial having an upper conical surface is built up in the bottom ofthe furnace combustion chamber 80.

The operating instrumentalities of the burner 15 are seen to comprisethe same parts as does the burner disclosed in Fig. 1, and include amotor 8S which is arranged with its shaft 88 in a vertical position andoperatively connected to a fan which rotates within a housing 92. Aflexible 20 coupling 94 connects the end of shaft 88 upon that side ofthe fan 90 opposite to the motor 86 to an oil pump adapted duringoperation to withdraw fuel oil from a tank and supply it underpressureto a fuel feed line 98. The fan 90 sup- 25 plies air underpressure through a draft tube |08 to a pressure or plenum chamber |02extending annularly about the head of the burner and centered withrespect to the central aperture in the refractory material oor 84 of thecombus- 30 tion chamber 80.

A cylindrical baille |04 extending around the burner head prevents theiair moving along the draft tube |00 from being blown directly againstone side of the burner head. To limit the flow 35 of air the upper endof the cylindrical baille |04 is spaced as at |08 from'the upper end ofthe plenum chamber |02 and air may flow only as indicated by the arrowsX in Fig. 7 through the space |06 and into an inside air chamber |08. 40The air, which has thus been forced to flowv through the space |06 hasconverted its velocity head into pressure head upon reaching the chamber|08 and since all parts of this chamber are under an equal pressure, theair will flow evenly 45 through three sets of apertures H0, ||2 and 4,as indicated by the arrows Y in Fig. 7, such apertures being provided ina burner head ||6 which l has its upper end positioned in the apertureformed in the bottom portion of the refractory 50 material floor 84. Theburner head ||6 and the bottom wall |I8 of the air chamber are fitted toone another so as to provide an air-tight joint Aat the point where thehead ||6 passes through the wall ||8. The air passing through the aper-55 tures ||0 is available to Wipe the surface oi' the oil nozzle 28which is inserted through the bottom of the head ||6 into the centralcavity |22 thereof along lines which form extensions of the elements ofconical surface 48 corresponding to the 60 surface 48 as appears moreclearly in Fig. 2. Air

vmay also pass through the apertures ||4 which correspond to theapertures 58 (Fig. 2) and perform the same function as the apertures 58.'I'hese apertures |14 may be arranged to extend 65 tangentially withrespect to the cylindrical surface of the expansion space adjacent thedischarge orifice 58 of the burner head'and may be so directed as togiverthe air either a clockwise or counterclockwise rotation. Theapertures ||4 70 might also be directed radially as are the apertures 58of Fig. 2.

Electrodes 32 are provided for initiating ignition of the oil and theiroperation is discontinued after combustion has been established,similarly l'75 to the electrodes described in connection with Figs. 1 to6.

In Figs. 8 and 9 a slightly different form of air supplying means isshown, the draft tube 5 thereof being arranged in a lower plane than isthe draft tube |00 shown in Fig. '7, being positioned to discharge airintora plenum chamber |24 which lies directly below the air chamber |26,corresponding to the air chamber |08 in Fig. 7, and being separatedtherefrom by a disc baille |28 centrally apertured at |30 to provide apassage for air from the chamber |24 to the chamber |26 as shown by thearrowsZ in Fig. 8. The fuel feed pipe 98 is sealed to the bottom wall|32 of the plenum chamber |24 at the point where it passes through thewall |32 to prevent'air from leaking through the Joint.

Fig. 9 illustrates more clearly the tangential arrangement of the airjets ||4 with respect to the cylindrical surface |34 of the expansionspace.

In Fig. 10 the head of the invention ls disclosed as applied to a burnerhaving a draft tube 24 provided on its inside surface with fins |40originally intended for the purpose of deflecting air in a spiral path.The mouth ofthe burner is provided with an inwardly curled edge |42which in the original burner served as a means for forming a cone of airfor surrounding the cone of fuel oil within the combustion chamber. Ahead 36', similar to the head 36 of Fig. 2 but minus the out-turnedflange40 thereof, may be positioned within the mouth of the burner withits outer face ush with the outer edge of the inside periphery of thecurled edge |42. The inwardly curled edge |42 thus serves to deflect airfor passage through the supplemental air supplying orifices 56 and theburner head 36' is supported upon the spiral fins |40 which line theinside of the draft tube 24. Set screws (not shown) may 40 be providedfor supporting and maintaining the v head 36' in its proper position. Anoil nozzle 26 and electrodes 32 may be employed, as in the constructionof Fig. 2.

With the constructions shown in Figs. 7 to 9,

45 it is possible to adapt the burner of the present invention for usein a wide variety of types of heating apparatus as it is possible, byvarying the size of the apertures ||4, to increase or decrease the anglewhich the flame may have with 50 respect to the vertical axis of theburner. This increase or decrease of the angle will also vary the amespeed and the distance which the flame will travel and may be arrangedto result in impingement of the products of combustion upon 55 the walls82 of the combustion chamber which form a heat transfer surface, andalso result in a. thorough wiping of the products of combustion againstthe combustion-chamber side of the walls 82 as they travel upwardlybefore being exhausted 60 through the flue.

It will be understood that the fuel combustion apparatus including thehead, electrodes,V spray nozzle and a portion of the draft tube might beemployed in connection with a furnace which a5 employs an exhaust fan inthe stack and relies upon the use of such exhaust fan to draw airthrough the draft tube. For the purposes of this invention, it isimmaterial whether the flow of air is caused by a positive pressure orby a pressure created by a vacuum, the only requirement being that apressure drop exist between the inside of the draft tube and thecombustion chamber.

While the supplemental apertures 56 have been described asconducting airat right angles to its path of movement through the draft tube, theseapertures might also be arranged so as to direct air slightly rearwardlyor in the direction of the oil nozzle 26, thus causing the air to take.a path which forms an acute angle with respect to a path of the airthrough the draft tube and burner head. It has been found that the acuteangular disposal of the orifices l56 as above described will also serveto retard the speed of the mixture and to stabilize the flame which ishovering in space off the end of the burner. that if the apertures 56are so -directed as to increase the speed of -the mixture flowing fromthe mouth of the burner that the iiame becomes unstable and the speed ofthe mixture increases beyond the rate of flame propagation and causesthe flame to be extinguished. When the supplemental air feedingapertures are tangentially arranged, as in Figs. 7 through 9, theycreate a vortex upon the at annular faces of the burner, thus tending topull the mixture issuing from the burner mouth outwardly and Atoincrease its angle. The resulting fire is very flat and spreading',which is ideal for the type of combustion chamber shown in Figs. '7 to9.

It will thus be seen that the combustion apparatus carries into effectthe objects of the invention as previously set forth and enables adomestic consumer to take full advantage of the high efciencies madeavailable by this burner idea. The right is reserved to make suchchanges in the details of construction and arrangement of parts as willfall within the purview of the attached claim which we make.

We claim:

Combustion apparatus comprising a draft tube adapted to be supplied withair under pressure from any suitable source, a cylindrical membersmaller than the inside dimension'of said draft tube and positionedwithin the mouth of said draft tube, a flange upon one end of `saidcylindrical member for engaging the end of said draft tube, saidcylindrical member being hollow and having arestricted orifice definingthe small end of a frustrum of a cone, a fuel discharge nozzlepositioned within said hollow member to discharge a cone of oil fog inthe direction of said orifice, the outer surface of said cylindricalmember being spaced from the inner surface of said draft'tube to formanair passage therebetween, said cylindrical member being provided witha. plurality of spaced orifices extending therethrough at right anglesto the central yaxis of the cylindrical memler between said flange andsaid restricted orifice and adjacent the surface surrounding saidrestricted orifice. c

MORITL L. MUELLER. GEORGE R. NEUMANN.

It has also been found ,A

